Phosphorus Containing Flame Retardants

ABSTRACT

Certain phosphonic acid salts heated at temperatures over 200° C. generate thermally stable, highly efficient flame retardant materials well suited for use as flame retardant additives in polymers. The flame retardants of the invention can be used as the sole flame retardant in a composition or in combination with other flame retardants, synergists or adjuvants.

This application claims benefit under 35 USC 119(e) of U.S. ProvisionalApplication No. 61/857,741 filed Jul. 24, 2013, the disclosure of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

Polymers, such as polyolefins, polyesters, polycarbonates, polyamides,polyurethanes, epoxy resins, and other thermoplastic or thermosetpolymer resins, are frequently made more flame retardant byincorporating therein a phosphorus-containing compound, ahalogen-containing compound or a mixture thereof. U.S. Pat. No.3,689,602, for example, discloses halogenated phosphoric acid esters asflame-retardant additives for plastics.

Some polymers are processed at high temperatures, for example 200° C.,220° C., 250° C. or higher, and many known flame retardants are notsuitable under these conditions because they are too volatile, notsufficiently thermally stable, have an adverse effect on processing,etc. Certain organophosphorus flame retardant compounds, such as somephosphate esters, can also exhibit a plasticizing effect which mayadversely affect mechanical properties of the polymers into which theyare added. In addition, compounds such as some phosphates are relativelyunstable to hydrolysis, which can result in undesired formation ofvarious phosphoric acid compounds.

Salts of phosphorus containing acids are known flame-retardantadditives, in particular for thermoplastic polymers. U.S. Pat. No.3,894,986 discloses flame retardant thermoplastic polyesters containingalkali salts of phosphonic acids, e.g., the mono sodium salt ofethane-phosphonic acid or a sodium salt of a mono-methyl ester of analkane-phosphonic acid. U.S. Pat. No. 4,972,011 discloses aluminum saltsof alkylphosphonic acids or mono-alkyl esters of alkane-phosphonicacids, i.e., salts of compounds of formula (la), wherein R is forexample methyl, ethyl, propyl or isopropyl etc., unsubstituted orsubstituted by one or more halo or hydroxy groups; and R′ is hydrogen,methyl, ethyl, propyl, or isopropyl.

DE 3833977 discloses metal salts of compounds of formula (la) preparedfrom reactions of dimethylmethylphosphinate and metal oxides orhydroxides in water at high pressures and temperatures from 120 to 200°C.; reactions run in aqueous solution under elevated pressures attemperatures up to 190° C. in an autoclave are exemplified. Adducts ofthese salts with amines such as ethylene diamine and melamine, and useof the adducts as flame retardants in thermoplastics are also disclosed.

Salts of phosphinic acids, i.e., compounds of formula (II) wherein R₁and R₂ are alkyl or carbon based aromatic, are also knownflame-retardant additives for thermoplastic polymers.

Salts wherein M is selected from Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr,Ce, Bi, Li, Na, K or protonated nitrogen base are known. For example,U.S. Pat. Nos. 5,780,534 and 6,013,707 disclose that calciumphosphinates and aluminum phosphinates of Formula (II) are particularlyeffective in polyester, for example, calcium and aluminum salts ofdimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinicacid, n-propylmethylphosphinic acid, n-propylethylphosphinic acid,di-n-propylphosphinic acid, diisopropylphosphinic acid ordiphenylphosphinic acid.

As is common with many flame retardant systems, the performance ofphosphorus containing acid derivatives can be enhanced by the presenceof other flame retardant agents, synergists and adjuvants. U.S. Pat. No.6,472,448 discloses flame retardant rigid polyurethane foam wherein acombination of oxalkylated alkylphosphonic acids and ammoniumpolyphosphate is present as flame retardant.

U.S. Pat. No. 6,365,071 discloses a synergistic flame retardantcombination for thermoplastic polymers, e.g., engineering plastics,especially for polyesters, comprising A) a phosphinic salt of theformula (II) above, e.g., aluminum dimethylphosphinate, aluminummethylethylphosphinate, and aluminum methylpropylphosphinate and B) anitrogen compound such as allantoin, i.e.,(2,5-dioxo-4-imidazolidinyl)urea, benzoguanamine, glycoluril, i.e.,tetrahydroimidazo[4,5-d]imidazole-2,5-dione, urea cyanurate, melaminecyanurate and melamine phosphate.

U.S. Pat. No. 6,255,371 discloses a flame retardant combinationcomprising, A) a phosphinate of formula (II) above, e.g., a diethylphosphinate where M is calcium, magnesium, aluminum and/or zinc, and B)condensation or reaction products of melamine e.g., melaminepolyphosphate, melam polyphosphate and melem polyphosphate.

U.S. Pat. No. 6,547,992 discloses a flame retardant combination forthermoplastic polymers comprising phosphinates and small amounts ofinorganic and/or mineral compounds which do not contain nitrogen. WO2012/045414 discloses a flame retardant composition comprising A) aphosphinic salt of the formula (II) above wherein M is selected from Mg,Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Li, Na, K or a protonatednitrogen base; B) a metal salt of phosphorous acid; and other optionalcomponents.

The phosphinates cited above, e.g., U.S. Pat. Nos. 6,365,071 and6,255,371, are said to be thermally stable, and neither decompose thepolymers during processing nor affect the process of preparing theplastic composition. The phosphinates are not volatile under thecustomary conditions of preparation and processing of thermoplasticpolymers. However, these materials are not necessarily suitable for usein all polymer systems and may create problems for processing or maylack the flame retardant effectiveness needed for certain polymers.There is still a need for flame retardants with greater efficiency atlower additive concentrations and improved processability for use inpreparing flame retardant polymer compositions with highly desirablephysical properties.

Phosphonic acid salts, i.e., salts metal salts of compounds according toformula (la), are also reported to be thermally stable, but this is ofcourse a relative term. As disclosed in US 2007/0029532, decompositionof such phosphonic acid salts is well known at temperatures encounteredduring processing of polyesters and polyamides, damaging the polymers inthe process.

U.S. Pat. No. 5,053,148 discloses heat resistant foams obtained byheating metal phosphonates or metal phosphonate precursors totemperatures of above 200° C. useful, e.g., as electrical and/or heatinsulation materials. Also disclosed is the use of this reaction toexpand or render porous other substrates. Such substrates include, forexample, thermoplastic polymers or plastics such as aromatic polyesters,polyethers, polysulfides, polyamides, polycarbonates, polyimides,polysiloxanes or polyphosphazenes, can be introduced into the foamingoperation as a mixture with metal phosphonates and/or their precursors.

While U.S. Pat. No. 5,053,148 may suggest that a porous polyamide may beproduced by heating a mixture of a metal phosphonate and a polyamideaccording to the “foaming process”, nothing in U.S. Pat. No. 5,053,148addresses or refutes the disclosure of US 2007/0029532 thatdecomposition of such phosphonic acid salts at high temperature gives“brittle compositions which are unusable” as an engineeringthermoplastic. Outside of suggesting that a porous foam may be producedby heating metal phosphonate and a polymer such as polyamide, U.S. Pat.No. 5,053,148 contains no mention of what the properties of such anunexemplified material might be.

The difficulty of thermally processing certain thermoplastic resins inthe presence of alkylphosphonic acid metal salts, and the poor physicalproperties of the polymer composition obtained thereby, has beenconfirmed by experimentation. However, it has now been found that theproducts obtained by heating certain alkylphosphonic acid metal salts,such as aluminum salts, calcium salts, zinc salts etc., at temperaturesin excess of 200° C. are thermally stable at temperatures above 400° C.and can be thermally incorporated onto thermoplastic polymer resinswithout adversely impacting the resulting physical properties of thepolymer composition obtained. Further, it is found that polymercompositions comprising the flame retardants of the invention, e.g.,thermoset or thermoplastic compositions, exhibit excellent flameretardant activity, either alone or in combination with other flameretardants, synergists or adjuvants.

SUMMARY OF THE INVENTION

Compounds of Formula (I)

wherein y is a number of from 1 to 7, e.g., from 1 to 4, M is a metalcation with a formal charge of (+)y, p is a number of from 1 to 7, e.g.,from 1 to 4, and R is e.g., alkyl, aryl, alkylaryl or arylalkyl, undergoreaction when heated at temperatures over 200° C., e.g., at temperaturesof 220° C. to 250° C. or higher, e.g. from about 200° C., 220° C. or250° C. to about 400° C. to form a different chemical species that istypically thermally stable to temperatures of 400° C. and higher and arewell suited for use as flame retardant additives in polymers. Thesereaction products have improved flame retardant properties and relativeto the compounds of formula (I) and are more readily processed intopolymer resins, such as polyamides, without negatively impacting thephysical property of the resin. The mechanism of action is uncertain atthis time, however, excellent and surprising results are obtained whenthe materials of the invention are used in conjunction with phosphinicacid salts, i.e., compounds of formula (II), and in a manner thatsuggests the possibility that the two materials may have different andcomplimentary activity.

This invention provides a flame retardant comprising the productobtained by the thermal treatment of compounds of formula (I), a processfor preparing the flame retardant, synergistic blends of the flameretardant with other flame retardants or flame retardant synergistse.g., blends of the flame retardant of the invention with phosphinicacid salts, and polymer compositions comprising the inventive flameretardant or synergistic blends.

Also provided is a method for preparing flame retardant polymers, whichmethod comprises heating compounds of formula (I) under conditions thatchemically transform said compounds to the thermally stable flameretardant material of the invention as described above, and thenincorporating the thus prepared thermally stable flame retardant into apolymer resin, e.g., by melt processing of the polymer and flameretardants at elevated temperature. A particular embodiment provides amethod wherein the thermally stable flame retardant prepared by heatingcompounds of formula (I) is added to a polymer resin along withphosphinic acid salts formula (II) and/or other synergists.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 displays the thermal analysis data of tris-[methylphosphonicacid] aluminum salt, prepared according to Comparative Example 1, whichis the starting material for the flame retardant material of Example 1.

FIG. 2 displays the thermal analysis data of the flame retardantmaterial of Example 1.

DESCRIPTION OF THE INVENTION

One embodiment of the invention is a flame retardant polymer compositioncomprising:

-   -   a) a thermoset or thermoplastic polymer, e.g., a thermoplastic        polymer,    -   b) from 1% to 50%, by weight based on the total weight of the        flame retardant composition of a flame retardant material        obtained by heating one, or more than one, phosphonic acid salt,        i.e., compounds of formula (I)

-   -   wherein R is an alkyl, aryl, alkylaryl or arylalkyl group, p is        a number of from 1 to 7, e.g., from 1 to 4, e.g., 1, 2, 3 or 4,        M is a metal, y is a number of from 1 to 7, e.g., from 1 to 4,        e.g., 1, 2, 3 or 4, often 2 or 3, so that M^((+)y) is a metal        cation where (+)y represents the charge formally assigned to the        cation,    -   at temperatures of 200° C. or higher, e.g., 220° C. or higher,        generally at temperatures of 250° C. or higher, e.g. from about        250° C. to about 400° C. or from about 260° C. to about 360° C.,        and    -   c) optional additional flame retardants or flame retardant        synergists.

For example, in formula (I), M^((+)y) where y is 1 represents amono-cation such as Li⁺, Na⁺ or K⁺, M^((+)y) where y is 2 represents adi-cation such as Mg⁺⁺, Ca⁺⁺ or Zn⁺⁺ and the like, M^((+)y) where y is 3represents a tri-cation such as Al⁺⁺⁺, etc. As is common withorganometallic species, the formulae are idealized and the startingmaterials may include complex salts or salts where certain atomicvalences are shared such as where a single oxygen anion is sharedbetween two metal cations, etc. Typically, the starting salt is chargedbalanced, that is, a compound of formula (I) wherein p=y, e.g., whenM^((+)y) is Na⁺, p is 1, when M is Al⁺⁺⁺ p is 3, etc.

While not wanting to be bound by theory, spectroscopic data and otheranalysis suggest that thermal treatment of a compound of formula (I)within the temperature treatment range of the invention generates amaterial comprising a compound that is believed to be genericallyrepresented by the empirical formula (IV) and complex dehydrationproducts thereof:

wherein R and M are as defined for formula (I), q is a number of from 1to 7, e.g., 1, 2 or 3, r is a number from 0 to 5, e.g., 0, 1 or 2, often0 or 1, y is a number of from 1 to 7, e.g., from 1 to 4, and n is1 or 2,provided that 2(q)+r=n(y). Typically, thermal treatment of a compound offormula (I) according to the invention generates a material comprisingmore than one compound, at least one of which is believed to begenerically represented by the empirical formula (IV) and complexdehydration products thereof. As is common with organometallic species,the formula (IV) is idealized and the product may include polymericsalts, complex salts, salts where certain atomic valences are shared,etc.

For example, when M is aluminum, i.e., when a compound of formula (I)wherein M is Al is heated according to the invention, elemental analysissuggests the formation of a product having an empirical formula (IV)wherein q is 1, r is 1, n is 1 and y is 3.

The flame retardant material obtained according to the invention is morethermally stable and exhibits greater flame retardant activity and hasimproved processability in a variety of polymer resins than the startingphosphonic acid salts of formula (I).

The polymer of flame retardant composition of the present invention maybe any polymer known in the art, such as polyolefin homopolymers andcopolymers, rubbers, polyesters, epoxy resins, polyurethanes,polyalkylene terephthalates, polysulfones, polyimides, polyphenyleneethers, styrenic polymers and copolymers, polycarbonates, acrylicpolymers, polyamides, polyacetals, epoxy resins and biodegradablepolymers. Mixtures of different polymers, such as polyphenyleneether/styrenic resin blends, polyvinyl chloride/ABS or other impactmodified polymers, such as methacrylonitrile and a-methylstyrenecontaining ABS, and polyester/ABS or polycarbonate/ABS and polyesterplus some other impact modifier may also be used. Such polymers areavailable commercially or made by means well known in the art.

The flame retardant of the invention is particularly useful inthermoplastic polymers that are processed and/or used at hightemperatures, for example, styrenic polymers including HIPS,polyolefins, polyesters, polycarbonates, polyamides, polyurethanes,polyphenylene ethers and the like.

For example, the polymer may be a polyester-series resin, a styrenicresin, a polyamide-series resin, a polycarbonate-series resin, apolyphenylene oxide-series resin, a vinyl-series resin, an olefinicresin, an acrylic resin, epoxy resin, or a polyurethane. The polymer canbe a thermoplastic or a thermoset resin and may be reinforced, e.g.,glass reinforced. More than one polymer resin may be present. Inparticular embodiments the polymer is an engineering polymer, e.g., athermoplastic or reinforced thermoplastic polymer, e.g., glassreinforced thermoplastic polymer, such as an optionally glass filledpolyester, epoxy resin or polyamide, for example, a glass-filledpolyester such as a glass filled polyalkylene terephthalate, or a glassfilled polyamide.

Polyester-series resins include homopolyesters and copolyesters obtainedby, for example, polycondensation of a dicarboxylic acid component and adiol component, and polycondensation of a hydroxycarboxylic acid or alactone component, for example, aromatic saturated polyester-seriesresin, such as polybutylene terephthalate or polyethylene terephthalate.

Polyamide-series resins include polyamides derived from a diamine and adicarboxylic acid; polyamides obtained from an aminocarboxylic acid, ifnecessary in combination with a diamine and/or a dicarboxylic acid; andpolyamides derived from a lactam, if necessary in combination with adiamine and/or a dicarboxylic acid. The polyamide also includes acopolyamide derived from at least two different kinds of polyamideconstituent components. Examples of polyamide-series resins includealiphatic polyamides such as nylon 46, nylon 6, nylon 66, nylon 610,nylon 612, nylon 11 and nylon 12, polyamides obtained from an aromaticdicarboxylic acid, e.g., terephthalic acid and/or isophthalic acid, andan aliphatic diamine, e.g., hexamethylenediamine ornonamethylenediamine, and polyamides obtained from both aromatic andaliphatic dicarboxylic acids, e.g., both terephthalic acid and adipicacid, and an aliphatic diamine, e.g., hexamethylenediamine, and others.These polyamides may be used singly or in combination.

In one embodiment of the invention, the polymer comprises a polyamidetypically processed at high temperatures, e.g., 300° C. or higher, insome embodiments 320° C. or higher, e.g. 340° C. or higher. Examples ofhigh temperature polyamides include thermoplastic resins such as nylon46, nylon 4T, nylon 6T/66 copolymers, nylon 9T and the like.

The flame retardant (b) exhibits excellent activity in polymer systemseither as the sole flame retardant or in combination with other flameretardants, synergists or adjuvants. The concentration of the inventiveflame retardant in the polymer composition is of course dependent on theexact chemical composition of the flame retardant, the polymer and othercomponents found in the final polymer composition. For example, whenused as the sole flame retarding component of a polymer formulation theinventive flame retardant may be present in a concentration of fromabout 1 to about 50%, e.g., 1 to 30%, by weight of the total weight ofthe final composition. Typically, when used as the sole flame retardantthere will be at least 2% of the inventive material present, for example3% or more, 5% or more, 10% or more, 15% or more, 20% or more or 25% ormore. In many embodiments, the inventive flame retardant is present inamounts up to 45%, while in other embodiments, the amount of inventiveflame retardant is 40% of the polymer composition or less, e.g., 35% orless. Obviously, when used in combination with other flame retardants orflame retardant synergists, less of the inventive material should beneeded.

Any known compounding techniques may be used to prepare the flameretardant polymer composition of the invention, for example, the flameretardant may be introduced into molten polymer by blending, extrusion,fiber or film formation etc. In some cases the flame retardant isintroduced into the polymer at the time of polymer formation or curing,for example, the flame retardant of the invention may be added to apolyurethane prepolymer prior to crosslinking or it may be added to apolyamine or alkyl-polycarboxyl compound prior to polyamide formation orto an epoxy mixture prior to cure.

Other embodiments of the invention are to the flame retardant materialand synergistic blends of the flame retardant material and othercomponents. The flame retardant of the invention is obtained by heatingone, or more than one, phosphonic acid salt, i.e., compounds of formula(I)

wherein R is an alkyl, aryl, alkylaryl or arylalkyl group, p is a numberof from 1 to 7, e.g., 1 to 4, e.g., 1, 2, 3 or 4, M is a metal, y is anumber of from 1 to 7, e.g., 1 to 4, e.g., 1, 2, 3 or 4, so thatM^((+)y) is a metal cation where (+)y represents the charge formallyassigned to the cation, at temperatures of 200° C. or higher, e.g., 220°C. or higher, generally at temperatures of 250° C. or higher, e.g. fromabout 250° C. to about 400° C. or from about 260° C. to about 360° C. Asstated above, the material generated by heating compounds of formula (I)at the listed temperature is believed to be compound or a mixture ofcompounds one or more of which is believed to be generically representedby the empirical formula (IV):

wherein R and M are as defined for formula (I), q is a number of from 1to 7, e.g., 1, 2 or 3, r is a number from 0 to 5, e.g., 0, 1 or 2, often0 or 1, y is a number of from 1 to 7, e.g., from 1 to 4, e.g., 1, 2, 3,or 4, and n is1 or 2, provided that 2(q)+r=n(y).

The phosphonic acid salts of formula (I) are known and various methodsfor their preparation are described in the art. For example, US2006/0138391 discloses compounds of formula (I) wherein R is hydrogen,C₁₋₁₈ alkyl, C₅₋₆ cycloalkyl, C₂₋₆ alkenyl, C₆₋₁₀ aryl, or C₇₋₁₁aralkyl,which alkyl, alkenyl, aryl, or aralkyl can be unsubstituted orsubstituted by halogen, hydroxyl, amino, C₁₋₄ alkylamino, di-C₁₋₄alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅ alkoxycarbonyl; and M can beselected from, e.g., Group IA, IB, IIA, IIB, IIIA, IVA, VA or VII of thePeriodic Table, for example Li, K, Na, Mg, Ca, Ba, Zn, Ge, B, Al, Cu,Fe, Sn or Sb, etc. It is noted that in US 2006/0138391 none of thecompounds corresponding to the formula (I) above were heated above 200°C. or compounded into a polymer resin at elevated temperature. The onlysalt actually exemplified in US 2006/0138391 was the aluminum salt ofmethyl methylphosphonic acid, i.e., the salt of a compound of formula(la) above wherein R and R′ are methyl, i.e.:

The starting material for the flame retardant of the present invention,i.e., compound of formula (I), can be conveniently selected from saltsdisclosed in US 2006/0138391 and elsewhere in the art. Compounds offormula (I) useful in the invention may also comprise other R groups notfound in US 2006/0138391, such as aryl substituted by alkyl, and it ispossible that compounds of formula (I) comprising metal cations notspecifically mentioned therein could be useful as starting materials.

In some embodiments of the invention, the salts of formula (I) comprisecompounds wherein R is C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, orC₇₋₁₈ arylalkyl group, wherein said groups are further substituted asdescribed in US 2006/0138391, but often R is unsubstituted C₁₋₁₂ alkyl,C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈ arylalkyl. For example, R issubstituted or unsubstituted, typically unsubstituted, C₁₋₆ alkyl, C₆aryl, C₇₋₁₀ alkylaryl, or C₇₋₁₂ arylalkyl, e.g., C₁₋₄ alkyl, C₆ aryl,C₇₋₁₉ alkylaryl, or C₇₋₁₀ arylalkyl.

While in the most general embodiments of the invention M^((+)y) may bealmost any metal cation, M is generally selected from Li, K, Na, Mg, Ca,Ba, Zn, Zr, Ge, B, Al, Si, Ti, Cu, Fe, Sn or Sb, for example, e.g., Li,K, Na, Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Sn or Sb, in many embodimentsM is Li, K, Na, Mg, Ca, Ba, Zn, Zr, B, Al, Sn or Sb, and in certainembodiments M is Al, Zn or Ca. For example, excellent results areachieved when M is Al or Ca.

R as alkyl is a straight or branched chain alkyl group having thespecified number of carbons and includes e.g., unbranched alky such asmethyl, ethyl, propyl, butyl, pentyl, hexyl heptyl, octyl, nonyl, decyl,undecyl, dodecyl, and unbranched alkyl such as iso propyl, iso-butyl,sec-butyl, t-butyl, ethyl hexyl, t-octyl and the like. For example, R asalkyl is methyl, ethyl, propyl, iso propyl, butyl, iso butyl, sec-buty,t-butyl, often R is methyl, ethyl, propyl or isopropyl, for examplemethyl.

Typically when R is aryl it is phenyl or naphthyl, for example, phenyl.Examples of R as alkylaryl include phenyl substituted by one or morealkyl groups, for example groups selected from methyl, ethyl, propyl,isopropyl, butyl, iso butyl, sec-buty, t-butyl, and the like. Examplesof R as arylalkyl, include for example, benzyl, phenethyl, styryl,cumyl, phenpropyl and the like.

In one embodiment R is methyl, ethyl, propyl, isopropyl, phenyl orbenzyl, e.g., methyl or phenyl.

In certain embodiments, for example, the starting material is a compoundof formula (I) wherein R is methyl, ethyl, propyl, isopropyl, benzyl orphenyl, M is Al, Zn or Ca, and p is 2 or 3. In one particular embodimentR is methyl, ethyl, propyl, isopropyl, or phenyl, p=3 and M is Al; inanother particular embodiment R is methyl, ethyl, propyl, isopropyl, orphenyl, p=2 and M is Zn or Ca, e.g., Ca.

The amount of time it takes to convert the phosphonic acid salts offormula (I) to the flame retardant of the invention will vary dependingon a variety of factors, including, e.g., the chemical structure of thestarting phosphonic acid salt, temperature of the reaction, otherreaction conditions etc. For example, higher temperatures can lead toquicker reaction times. It is believed that water is produced in duringthe reaction and the presence of a water absorbent or vacuum may alsoreduce reaction times. Design of the reaction vessel, the presence ofother materials during heating, etc., can also impact the time ofreaction.

Good conversion is frequently obtained by heating a phosphonic acid saltof formula (I) at temperatures of e.g., at least 200° C., 220° C., 250°C. or higher, for a time of 20 hours or less, typically less than 12hours. In certain circumstances the time can be extremely short, forexample, use of higher temperatures, e.g., 250° C. to 400° C. ortemperatures above 400° C., in a reaction vessel or environment thatmakes heat transfer to the starting material highly efficient cangreatly reduce reaction times to, for example, less than 0.2 hour, 0.1hour, or 0.01 hours or less and complete reactions times measured inseconds or less are possible.

Generally full conversion to the flame retardant of the invention isobtained by heating the starting phosphonic acid salt at temperatures offrom about 200° C. to about 400° C. for from about 0.01 or 0.2 to about20 hours, often about 0.1 or 0.2 to about 12 hours, or from about 1 toabout 8 hours, although as stated above the amount of time for fullconversion will depend on the temperature. For example, heating thephosphonic acid salt of formula (I) at from about 250° C. to about 400°C. will require less than 12 hours of heating, e.g., from about 1 to 8hours. Excellent results have been obtained when the starting phosphonicacid salt is heated at from about 260° C. to about 340° C. for about 1to 6 hours, e.g., for about 2 to about 6 hours.

For example, tris-[methylphosphonic acid] aluminum salt, i.e. a watersoluble solid compound of formula (III) wherein R is methyl, is heatedat a temperature of from 250 to about 320° C. for about 2 to about 6hours to form a solid material that is, in contrast to the startingmaterial, not soluble in water and stable at temperatures in excess of400° C. Higher reaction temperatures can be used, however, as seen inthe examples, heating at about 280° C. for 4 hours yields excellentresults.

Likewise, heating tris-[ethylphosphonic acid] aluminum salt, i.e. thecompound of formula (III) wherein R is ethyl, or tris-[phenylphosphonicacid] aluminum salt, i.e. the compound of formula (III) wherein R isphenyl, under similar conditions leads to analogous ethyl and phenylcontaining flame retardant material.

Generally, the selected phosphonic acid metal salt or mixture of saltsused as starting material is heated on its own, i.e., in the absence ofother materials. However, one could heat these salts in the presence ofe.g., an inert carrier, another flame retardant, or other potentialadditives, etc., although the presence of added water is typicallyavoided as it is believed that water is eliminated from the startingmaterial during reaction. For example, the starting materials could bemixed with other flame retarding materials, polymer stabilizers, orother known polymer additives before heating above 200° C. The thermaltransformation of the salts could also take place in the presence of asmall amount of polymer as an inert carrier, however, one must becareful to avoid a situation wherein the conversion of the starting saltis impeded by the presence of other materials. For example, a polymer orother material may melt under the reaction temperatures and coat thesalt, or even react with the salt, producing undesired consequences.

In many embodiments a compound of formula (I) undergoes thermaltreatment in the absence of other components. If a polymer or otherinert carrier is present during the reaction it is present in an amountthat is less than the amount of phosphonic acid metal salt, e.g., lessthan 50% or less than 25% by weight of the combination of phosphonicacid metal salt and polymer, typically less 10%, for example less than5% or from 0 to 2% by weight. As the salt of formula (I) is believed toliberate water in the reaction it is advisable to avoid heating the saltabove 200° C. in the presence of a material that is unstable in thepresence of water at high temperature including polymers capable ofundergoing hydrolysis.

According to the present invention, the phosphonic acid metal salt offormula (I) is thermally transformed to a different, more thermallystable flame retardant material before it is incorporated into the bulkof the polymer that it is to protect. Contrary to the salts of formula(I), which are also known as flame retardants, the present flameretardants are stable at processing temperatures above 200° C. and donot undergo reaction which may have a negative impact on, e.g., polymerssuch as polyesters and polyamides which contain linkages susceptible toreaction and cleavage.

For example, polyalkylene phthalates, polyamides and many othercondensation polymers are processed at high temperatures. At hightemperatures, salts of formula (I) undergo reactions that apparentlyliberate water, which could lead to hydrolysis at the ester or amidelinkages, causing chain cleavage and loss of molecular weight anddesired physical properties. In Comparative Example 1, attempts weremade to compound a salt of formula (I) into a glass filled polyamide atelevated temperature resulting in polymer degradation. While it is notknown whether the elimination of water during the thermal treatment ofthe salts of formula (I) was responsible for the observed degradation,flame retardants of the invention from Examples 1, 2 and 3 weresuccessfully incorporated into the same glass filled polyamide withoutnoticeable degradation.

The flame retardant of the invention may be used with a variety of otherflame retardants, synergists or flame retardant adjuvants as known inthe art. For example, the flame retardant of the invention may beformulated with one or more materials selected from: carbon black,graphite, carbon nanotubes, silicones; polyphenylene ether (PPE),phosphine oxides and polyphosphine oxides, e.g., benzylic phosphineoxides, poly benzylic phosphine oxides and the like;

melamine, melamine derivatives and condensation products, melamine saltssuch as, but not limited to, melamine cyanurate, melamine borate,melamine phosphates, melamine metal phosphates, and the like;

inorganic compounds including clays, metal salts such as hydroxides,oxides, oxide hydrates, borates, carbonates, sulfates, phosphates,phosphites, hypophosphites, silicates, mixed metal salts, etc., e.g.,talc and other magnesium silicates, calcium silicate, aluminosilicate,aluminosilicate as hollow tubes (DRAGONITE), calcium carbonate,magnesium carbonate, barium sulfate, calcium sulfate, HALLOYSITE orboron phosphate, calcium molybdate, exfoliated vermiculite, zincstannate, zinc hydroxystannate, zinc sulfide and zinc borate, zincmolybdate (KEMGARD 911A/B), zinc phosphate (KEMGARD 981), magnesiumoxide or hydroxide, aluminum oxide, aluminum oxide hydroxide (Boehmite),aluminum trihydrate, silica, tin oxide, antimony oxide (III and V) andoxide hydrate, titanium oxide, and zinc oxide or oxide hydrate,zirconium oxide and/or zirconium hydroxide and the like.

Unless otherwise specified, in the context of the present application,the term “phosphate” when used as a component in a “phosphate salt”,such as in metal phosphate, melamine phosphate, melamine metalphosphate, etc., refers to a phosphate, hydrogen phosphate, dihydrogenphosphate, pyrophosphate, polyphosphate, or a phosphoric acidcondensation products anion or polyanion.

Likewise, unless otherwise specified, in the context of the presentapplication, the term “phosphite” when used as a component in a“phosphite salt”, such as in metal phosphite, etc., refers to aphosphite or hydrogen phosphite.

The flame retardant of the invention may also be formulated with otherflame retardants such as halogenated flame retardants, alkyl or arylphosphine oxide flame retardants, alkyl or aryl phosphate flameretardants, alkyl or aryl phosphonates, alkyl or aryl phosphinates, andsalts of alkyl or aryl phosphinic acid. One particular embodimentprovides a synergistic mixture of the flame retardant of the inventionand a phosphinic salt of formula (II), e.g., an aluminumtris(dialkylphosphinate).

Thus, in many embodiments the flame retardant polymer compositionaccording to the invention comprise the polymer (a), the flame retardant(b), and further comprise (c) one or more additional flame retardants,and/or one or more synergists or flame retardant adjuvants.

For example, in some embodiments the flame retardant polymer compositioncomprises one or more additional flame retardants, e.g., halogenatedflame retardants, phosphine oxide flame retardants, alkyl or arylphosphonates, or salts of alkyl or aryl phosphinates, e.g., an aluminumtris(dialkylphosphinate) such as aluminum tris(diethylphosphinate).

In some embodiments the flame retardant polymer composition comprisesone or more synergists or flame retardant adjuvants, e.g., melamine,melamine derivatives and condensation products, melamine salts,phosphine oxides and polyphosphine oxides, metal salts such ashydroxides, oxides, oxide hydrates, borates, phosphates, phosphites,silicates and the like, e.g. aluminum hydrogen phosphite, melem or amelamine metal phosphate, e.g., a melamine metal phosphate wherein themetal comprises aluminum, magnesium or zinc. In particular embodimentsthe one or more additional flame retardant, synergist or flame retardantadjuvant comprises an aluminum tris(dialkylphosphinate), aluminumhydrogen phosphite, methylene-diphenylphosphine oxide-substitutedpolyaryl ether, xylylenebis(diphenylphosphine oxide),4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, ethylenebis-1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane,melem, or dimelamine zinc pyrophosphate.

One particular embodiment is to a synergistic mixture comprising theflame retardant of the invention and aluminum tris(diethylphosphinate).

For example, the flame retardant of the invention may be combined withan additional flame retardant, synergist or adjuvant in a range of 100:1to 1:100 by weight of inventive flame retardant to the total weight ofadditional flame retardant, synergist and adjuvant. Depending on theadditional flame retardant, synergist or adjuvant, excellent can beobtained using a range of 10:1 to 1:10 by weight of flame retardant toadditional flame retardant, synergist and/or adjuvant, for example,weight ratios ranging from 7:1 to 1:7, 6:1 to 1:6, 4:1 to 1:4, 3:1 to1:3 and 2:1 to 1:2 are used to good benefit. The inventive flameretardant is typically the majority component in such a combination,e.g., a 10:1 to 1.2:1 ratio or a 7:1 to 2:1 ratio by weight of theinventive flame retardant material to additional flame retardant,synergist and/or adjuvant, but the inventive material can also be theminor component of the mixture, e.g., a 1:10 to 1:1.2 ratio or a 1:7 to1:2 ratio of flame retardant to additional flame retardant, synergistand/or adjuvant synergist.

The flame retardant polymer composition of the invention will alsotypically contain one or more of the common stabilizers or otheradditives frequently encountered in the art such as phenolicantioxidants, hindered amine light stabilizers (HALS), the ultravioletlight absorbers, phosphites, phosphonites, alkaline metal salts of fattyacids, hydrotalcites, metal oxides, borates, epoxidized soybean oils,the hydroxylamines, the tertiary amine oxides, lactones, thermalreaction products of tertiary amine oxides, thiosynergists, basicco-stabilizers, for example, melamine, melem etc., polyvinylpyrrolidone,dicyandiamide, triallyl cyanurate, urea derivatives, hydrazinederivatives, amines, polyamides, polyurethanes, hydrotalcites, alkalimetal salts and alkaline earth metal salts of higher fatty acids, forexample, Ca stearate, calcium stearoyl lactate, calcium lactate, Znstearate, Zn octoate, Mg stearate, Na ricinoleate and K palmirate,antimony pyrocatecholate or zinc pyrocatecholate, nucleating agents,clarifying agents, etc.

Other additives may also be present, for example, plasticizers,lubricants, emulsifiers, pigments, dyes, optical brighteners, otherflameproofing agents, anti-static agents, blowing agents, anti dripagents, e.g., PTFE, and the like.

Optionally the polymer may include fillers and reinforcing agents, forexample, calcium carbonate, silicates, glass fibers, talc, kaolin, mica,barium sulfate, metal oxides and hydroxides, carbon black and graphite.Such fillers and reinforcing agents may often be present at relativelyhigh concentrations, including formulations where the filler orreinforcement is present in concentrations of over 50 wt % based on theweight of the final composition. More typically, fillers and reinforcingagents are present from about 5 to about 50 wt %, e.g., about 10 toabout 40 wt % or about 15 to about 30 wt % based on the weight of thetotal polymer composition.

EXAMPLES Comparative Example 1

To a solution of 96.0 g methylphosphonic acid (1.00 mol) in 210 mLdeionized water is slowly added 54.1 g aluminum ethoxide (0.334 mol)under nitrogen. The reaction mixture is then stirred at room temperaturefor 16 h. The solution is subsequently concentrated and dried at 100° C.in vacuo to afford a clear, colorless solid. Thermal analysis, as shownin FIG. 1, indicated the loss of one mole of water starting atapproximately 250° C. Elemental analysis: 29.8% P, 9.0% Al; calc'd 29.8%P, 8.7% Al.

20 parts of the salt and 30 parts glass were compounded into 50 partspolyamide 66 using a Haake Rheocord 90 equipped with a three pieceBrabender measuring head. A decrease in torque was observed duringcompounding, which could signify polymer degradation, resulting in amaterial resembling wet newspaper that was friable upon cooling anddusty after grinding. Analysis of the compounded material, which couldnot be molded, by gel permeation chromatography (GPC) and differentialscanning calorimetry (DSC) provided additional evidence of degradation.

Example 1 Flame Retardant from Methylphosphonic Acid Aluminum Salt,FR-INV1

To a cooled solution of 48.0 g methylphosphonic acid (500 mmol) in 210ml deionized water is slowly added 27.0 g aluminum ethoxide (167 mmol)under nitrogen. The reaction is then allowed to warm to room temperatureand is stirred for 16 h. The solution is subsequently concentrated anddried at 100° C. in vacuo to afford a clear, colorless solid. Thermalanalysis as indicated the loss of one mole of water starting at 250° C.The colorless solid was heated for 4 h at 280° C. resulting in anoff-white solid that is stable to >400° C., as shown in FIG. 2.Elemental analysis: 31.5% P, 9.0% Al.

Comparative Example 2

To a stirred solution of 37.9 g ethylphosphonic acid (344 mmol) in 150mL deionized water is added a solution of 27.7 g aluminum chloridehexahydrate (115 mmol) in 150 mL deionized water. The solution is thenconcentrated in vacuo to remove water and HCl. Drying at 130° C. in avacuum oven affords a white powder. Thermal analysis indicated the lossof one mole of water starting at approximately 200° C. Elementalanalysis: 25.0% P, 6.9% Al.

20 parts of the salt and 30 parts glass were compounded into 50 partspolyamide 66 using a Haake Rheocord 90. Low torque was observedthroughout compounding, which could signify polymer degradation, withthe formulation swelling out of the bowl towards the end of the runresulting in a material that foamed due to escaped gases and that wasfriable upon cooling and dusty after grinding. Analysis of thecompounded material, which could not be molded, by GPC and DSC providedadditional evidence of degradation.

Example 2 Flame Retardant from Ethylphosphonic Acid Aluminum Salt,FR-INV2

To a stirred solution of 149.5 g ethylphosphonic acid (1.36 mol) in 500mL deionized water is added a solution of 109.3 g aluminum chloridehexahydrate (.453 mol) in 250 mL deionized water. The solution is thenconcentrated and dried at 130° C. in vacuo to remove water and HCl.Thermal analysis indicated the loss of one mole of water starting at180° C. Heating the dried salt for 3 h at 225° C. affords a white powderthat is stable to approximately 400° C. Elemental analysis: 27.3%P, 7.6%Al.

Example 3 Flame Retardant from Ethylphosphonic Acid Calcium Salt,FR-INV3

To a stirred solution of 52.1 g ethylphosphonic acid (473 mmol) in 250mL deionized water is slowly added 17.5 g calcium hydroxide (236 mmol).The solution is then concentrated and dried at 100° C. in vacuo. Thermalanalysis indicated the loss of one mole of water staring at 220° C.Heating the dried salt for 3 h at 290° C. affords a white powder that isstable >400° C. Elemental analysis: 25.3% P, 16.3% Ca.

Formulations comprising flame retardants from Examples 1, 2 and 3 andvarious synergists were compounded into polyamide 66 with glass using aHaake Rheocord 90 and molded with a BabyPlast Mini-Molder into 1/16″bars which were subjected to standard UL 94 Vertical Burn Test.Formulations and results are listed in Table 1 below.

TABLE 1 FR Data Formulation 1 2 3 4 5 6 7 8 9 10 11 12 Nylon 66 56.3 4553.8 57.5 50.7 53 50.3 51.7 46.3 53.8 54.4 45 Glass 30 30 30 30 30 30 3030 30 30 30 30 FR-INV1 13.7 25 13.7 10 13.7 13.7 13.7 13.7 13.7 13.7FR-INV2 15.6 FR-INV3 15 SYN1 2.5 2.5 SYN2 5.6 SYN3 3.3 SYN4 6 SYN5 4.6SYN6 10 SYN7 2.5 SYN8 10 UL 94 V-1 V-0 V-0 V-1 V-0 V-0 V-0 V-0 V-0 V-1V-0 V-0 Synergists used in the FR formulations: SYN1: Aluminumtris(diethylphosphinate), Exolit ® OP 1230

SYN2: Methylene-diphenylphosphine oxide-substituted polyaryl ether

SYN3: p-Xylylenebis(diphenylphosphine oxide)

SYN4: 4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl

SYN5: 1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane

SYN6: Melem, Delacal ® NFR HP

SYN7: Aluminum hydrogen phosphite Al₂(HPO₃)₃ SYN8: Dimelamine zincpyrophosphate, Safire ® 400

What is claimed:
 1. A flame retardant polymer composition comprising: a)a thermoset or thermoplastic polymer, b) from 1% to 50%, by weight basedon the total weight of the flame retardant polymer composition, of aflame retardant material obtained by a process comprising heating attemperatures of about 200° C. or higher from about 0.01 hour to about 20hours one or more than one compound of formula (I)

wherein R is C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C_(m)alkoxycarbonyl; M is a metal, y is a number of from 1 to 4 so thatM^((+)y) is a metal cation where (+)y represents the charge formallyassigned to the cation, and p is a number of from 1 to
 4. 2. The flameretardant polymer composition according to claim 1 wherein M in formula(I) is Li, K, Na, Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Sn or Sb.
 3. Theflame retardant polymer composition according to claim 1 wherein M informula (I) is Al or Ca.
 4. The flame retardant polymer compositionaccording to claim 1 wherein in formula (I) R is unsubstituted C₁₋₆alkyl, C₆ aryl, C₇₋₁₀ alkylaryl, or C₇₋₁₂ arylalkyl.
 5. The flameretardant polymer composition according to claim 4 wherein R is methyl,ethyl, propyl, isopropyl, benzyl or phenyl.
 6. The flame retardantpolymer composition according to claim 5 wherein M in formula (I) is Alor Ca.
 7. The flame retardant polymer composition according to claim 1wherein the thermoset or thermoplastic polymer comprises one or more ofa polyolefin homopolymer, polyolefin copolymer, rubber, epoxy resin,polyester, polyurethane, polysulfone, polyimide, polyphenylene ether,styrenic polymer, styrenic copolymer, polycarbonate, acrylic polymer,polyamide, polyacetal, epoxy resin, biodegradable polymer or a blendthereof.
 8. The flame retardant polymer composition according to claim 1wherein the thermoset or thermoplastic polymer comprises one or more ofa polyphenylene ether/styrenic resin blend, ABS, polyvinyl chloride/ABSblend, methacrylonitrile containing ABS, a-methylstyrene containing ABS,polyester/ABS, polycarbonate/ABS, impact modified polyester or impactmodified polystyrene.
 9. The flame retardant polymer compositionaccording to claim 7 wherein the thermoset or thermoplastic polymercomprises one or more of a styrenic polymer, polyolefin, polyester,epoxy resin, polycarbonate, polyamide, or polyurethane.
 10. The flameretardant polymer composition according to claim 7 wherein the thermosetor thermoplastic polymer further comprises a reinforcing agent.
 11. Theflame retardant polymer composition according to claim 9 wherein thethermoset or thermoplastic polymer comprises a polyalkyleneterephthalate, HIPS, epoxy resin or polyamide, which thermoset orthermoplastic polymer optionally further comprises a reinforcing agent.12. The flame retardant polymer composition according to claim 11wherein the thermoset or thermoplastic polymer comprises polybutyleneterephthalate, polyethylene terephthalate, glass filled polybutyleneterephthalate, glass filled polyethylene terephthalate, a glassreinforced epoxy resin, a thermoplastic polyamide or a glass filledthermoplastic polyamide.
 13. The flame retardant polymer compositionaccording to claim 12 wherein the thermoplastic polyamide or glassfilled thermoplastic polyamide comprises nylon 46, nylon 4T, nylon 6T/66copolymer, or nylon 9T.
 14. The flame retardant polymer compositionaccording to claim 6 wherein the thermoset or thermoplastic polymercomprises one or more of a polyolefin homopolymer, polyolefin copolymer,rubber, polyester, polyurethane, polysulfone, polyimide, polyphenyleneether, styrenic polymer, styrenic copolymer, polycarbonate, acrylicpolymer, polyamide, polyacetal, epoxy resin, biodegradable polymer or ablend thereof.
 15. The flame retardant polymer composition according toclaim 14 wherein the thermoset or thermoplastic polymer comprises one ormore of a styrenic polymer, polyolefin, polyester, epoxy resin,polycarbonate, polyamide, or polyurethane.
 16. The flame retardantpolymer composition according to claim 14 wherein the thermoset orthermoplastic polymer further comprises a reinforcing agent.
 17. Theflame retardant polymer composition according to claim 15 wherein thethermoset or thermoplastic polymer comprises a polyalkyleneterephthalate, HIPS, epoxy resin or polyamide, which thermoset orthermoplastic polymer optionally further comprises a reinforcing agent.18. The flame retardant polymer composition according to claim 17wherein the thermoset or thermoplastic polymer comprises polybutyleneterephthalate, polyethylene terephthalate, glass filled polybutyleneterephthalate, glass filled polyethylene terephthalate, a glassreinforced epoxy resin, a thermoplastic polyamide or a glass filledthermoplastic polyamide.
 19. The flame retardant polymer compositionaccording to claim 18 wherein the thermoplastic polyamide or glassfilled thermoplastic polyamide comprises nylon 46, nylon 4T, nylon 6T/66copolymer, or nylon 9T.
 20. The flame retardant polymer compositionaccording to claim 1 further comprising (c) one or more additional flameretardants, and/or one or more synergists or flame retardant adjuvants.21. The flame retardant polymer composition according to claim 20comprising one or more additional flame retardants, wherein the one ormore additional flame retardants comprise halogenated flame retardants,alkyl or aryl phosphine oxide flame retardants, alkyl or aryl phosphateflame retardants, alkyl or aryl phosphonates, alkyl or arylalkylphosphinates, or salts of alkyl or aryl phosphinic acid.
 22. Theflame retardant polymer composition according to claim 21 wherein theone or more additional flame retardants comprise an aluminumtris(dialkylphosphinate).
 23. The flame retardant polymer compositionaccording to claim 20 comprising one or more synergists or flameretardant adjuvants, wherein the one or more synergists or flameretardant adjuvants comprise melamine, melamine derivatives, melaminecondensation products, melamine salts, phosphine oxides, polyphosphineoxides, or metal hydroxides, oxides, oxide hydrates, borates,phosphates, phosphites or silicates.
 24. A flame retardant compositionaccording to claim 23 wherein the one or more synergists or flameretardant adjuvants comprise aluminum hydrogen phosphite, benzylicphosphine oxides, poly benzylic phosphine oxides, melem or melaminemetal phosphate wherein the metal comprises aluminum, zinc or magnesium.25. The flame retardant polymer composition according to claim 20comprising (c) one or more additional flame retardant, synergist orflame retardant adjuvant, wherein the one or more additional flameretardant, synergist or flame retardant adjuvant comprises an aluminumtris(dialkylphosphinate), aluminum hydrogen phosphite,methylene-diphenylphosphine oxide-substituted polyaryl ether,xylylenebis(diphenylphosphine oxide),1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane, a4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, melem, or dimelaminezinc pyrophosphate.
 26. The flame retardant polymer compositionaccording to claim 14 comprising (c) one or more additional flameretardant and/or synergist or flame retardant adjuvant.
 27. The flameretardant polymer composition according to claim 26 comprising (c) oneor more additional flame retardant, synergist or flame retardantadjuvant, wherein the one or more additional flame retardant, synergistor flame retardant adjuvant comprises an aluminumtris(dialkylphosphinate), aluminum hydrogen phosphite, amethylene-diphenylphosphine oxide-substituted polyaryl ether, axylylenebis(diphenylphosphine oxide),1,2-bis-(9,10-dihydro-9-oxy-10-phosphaphenanthrene-10-oxide)ethane, a4,4′-bis(diphenylphosphinylmethyl)-1,1′-biphenyl, melem, or dimelaminezinc pyrophosphate.
 28. A process for increasing the flame resistance ofa polymer comprising heating at temperatures of about 200° C. or higherone or more than one compound of formula (I)

wherein R is C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅alkoxycarbonyl; M is a metal, y is a number of from 1 to 4 so thatM^((+)y) is a metal cation where (+)y represents the charge formallyassigned to the cation, and p is a number of from 1 to 4; to prepare aflame retardant material followed by incorporating the flame retardantmaterial into a polymer resin, optionally with one or more additionalflame retardant, synergist or flame retardant adjuvant.
 29. A flameretardant comprising a material obtained by a process comprising heatingat temperatures of about 200° C. or higher, one or more than onecompound of formula (I)

wherein R is C₁₋₁₂ alkyl, C₆₋₁₀ aryl, C₇₋₁₈ alkylaryl, or C₇₋₁₈arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl areunsubstituted or are substituted by halogen, hydroxyl, amino, C₁₋₄alkylamino, di-C₁₋₄ alkylamino, C₁₋₄ alkoxy, carboxy or C₂₋₅alkoxycarbonyl; M is a metal, y is a number of from 1 to 7 so thatM^((+)y) is a metal cation where (+)y represents the charge formallyassigned to the cation, and p is a number of from 1 to
 7. 30. The flameretardant according to claim 29 wherein in the compound of formula (I)that is is heated at temperatures of about 200° C. or higher, M isaluminum, y is 3 and p is 3.